The invention relates to a process for hardening an annular groove of a piston head of a steel piston of an internal combustion engine and a piston produced by the process.
A process for hardening an annular groove of a piston head of a steel piston of an internal combustion engine by means of laser beams is known from EP 1 173 624 B1. In this process, a laser beam for hardening the annular grooves is directed at the piston in an approximately circumferential direction. As a result of the approximately tangential beam line, reflection of the laser beams in the direction of the bottom of the groove and, with a correspondingly small angle of incidence, a reflection against the oppositely located groove flanks is prevented. However, the disadvantage is that for adequate hardening, the laser beam must possess high energy with the result that the hardening process can be carried out only very slowly. As a result, when producing such pistons, cycle time in serial production is disadvantageously slowed. Additionally, because of the high laser energy is disadvantageous in that there is a risk of distortion of the piston head area.
It would be desirable to provide a process and a piston in which the hardening procedure using laser beams, which is intrinsically satisfactory, is retained, but at the same time the prior art disadvantages are avoided.